I need to create reports around tag usage and unanswered posts. What're the different mechanisms available to access this data?
There are 4 options:
Use SEDE (Stack Exchange Data Explorer), which allows you to easily query the data. You can download the queried rows, however it does not allow you to run queries locally and can only be used manually.
Use SE API, which allows you to query some things of Stack Overflow over REST calls.
Download a public release of the SO data dump and use historical data.
Use the Stack Exchange public dataset on Google BigQuery